The metabolic pathway of the fermentation of ethylene glycol and propylene glycol by Clostridium glycolicum was investigated and the levels of the five enzymes involved were determined. Diol dehydratase, the first enzyme in the pathway, was found to be membrane bound and very sensitive to oxygen. The enzyme was subjected to various treatments in order to solubilize it from its matrix. Only limited proteolysis was found to release small amounts of enzyme activity from the membrane. Addition of different compounds known to affect the activity of cobamide coenzyme dependent enzymes had no influence on the activity of diol dehydratase, suggesting a novel reaction mechanism. The enzyme was strongly inhibited by several compounds, among them radical scavengers such as hydroxylamine and hydroxyurea. Preliminary EPR experiments in combination with the inhibition experiment indicate the possible involvement of a radical in the catalytic mechanism.